Selective detection of clinically relevant Gram-negative bacteria using a colistin-functionalized ISFET biosensor

Area of Science:

• Biosensing and Nanotechnology
• Microbiology
• Materials Science

Background:

• Rapid and selective detection of Gram-negative bacteria is crucial for clinical diagnostics, food safety, and environmental monitoring.
• Existing methods often require complex procedures or lack specificity.
• Development of sensitive, label-free biosensors is highly desirable.

Purpose of the Study:

• To develop and evaluate a label-free Ion-Sensitive Field-Effect Transistor (ISFET) sensor for the selective detection of Gram-negative bacteria.
• To characterize the sensor's performance, including its detection limit, linearity, and stability.
• To assess the sensor's applicability in real-world samples.

Main Methods:

• Fabrication of a p-type silicon/SiO2 ISFET platform modified with zinc oxide (ZnO) and colistin.
• Testing the sensor's response to various Gram-negative bacteria (e.g., Escherichia coli, Pseudomonas aeruginosa) and Gram-positive bacteria (e.g., Staphylococcus aureus) as controls.
• Analysis of sensor performance using drain-source current measurements, standard curves, and real-sample assays.

Main Results:

• The ISFET sensor demonstrated measurable drain-source current changes upon binding of Gram-negative bacteria.
• Low limits of detection were achieved, ranging from approximately 137 CFU/mL for E. coli to 289 CFU/mL for P. aeruginosa.
• The sensor exhibited good stability over 14 days and showed high recovery rates in spiked bottled water and urine samples.

Conclusions:

• The developed ZnO and colistin-modified ISFET sensor provides a promising platform for the selective and sensitive detection of Gram-negative bacteria.
• The label-free nature and low detection limits make it suitable for various applications.
• Further validation in diverse real-world conditions could establish its clinical and environmental utility.